The present invention relates to a magnetic disk device, or in particular to a magnetic disk device comprising a magnetic head support mechanism including a coarse actuator and a micro actuator.
In the conventional magnetic disk device, an actuator having only a voice coil motor (VCM) mounted thereon is used as a means for driving the head. With the recording density of the magnetic disk device ever on the increase, it has been desired to improve the head positioning accuracy to reduce the track pitches. For this purpose, the servo band of the head positioning control system is required to be improved to at least 1 kHz. It has become difficult, however, to realize the servo band of 1 kHz or more with the conventional system for driving the head only with the VCM due to the effect of the resonance mode of the actuator.
In view of this, JP-A-4-368676 proposes the use of a dual-stage actuator, for example, including a coarse actuator and a micro actuator for inching the head as a means for driving the VCM.
Generally, with the magnetic disk device, the waiting (idle mode) time for performing the operation of following the track without any instruction from a host system is overwhelmingly longer than the execution time for performing the recording/reproducing operation or the operation of accessing a track (seek operation) in response to an instruction from the host system. The coarse actuator and the fine actuator continued in operation to perform the following operation in idle mode poses the problem of a shortened service life of the micro actuator. The relation between the service life of a piezo actuator used as a micro actuator and the operation time is described, for example, in xe2x80x9cStudy on Lifetime Prediction Method for Piggyback PZT Actuator, 2000 Asia-Pacific Magnetic Recording Conference, WA3-01/02, 2000xe2x80x9d by Nakamura, et al.
The present invention has been developed in view of the problem described above, and the object thereof is to improve the service life of the micro actuator by stopping the feedback control operation of the micro actuator and thus reducing the operation time of the micro actuator as far as possible in idle mode in the absence of a data access command from the host system and thereby to provide a reliable magnetic disk device.
Another object of the present invention is to provide a magnetic disk device which can perform the operation of quick restoration from the inactive state of the micro actuator.
In order to achieve the objects described above, according to the present invention, there is provided a magnetic disk device comprising a micro actuator for supporting a head to read or write information from or into a disk and performing a micro positioning operation, a coarse actuator for positioning the head by coarsely moving the support mechanism carrying the micro actuator, a control means for controlling the micro actuator and the coarse actuator based on the servo information read by the head and a host controller for giving an command to read or write information, wherein the positioning operation of the micro actuator is stopped in the case where the host controller determines that the operation is in idle mode.